title: Harnessing molecular excited states with Lanczos chains.
abstract: The recursion method of Haydock, Heine and Kelly is a powerful tool for calculating diagonal matrix elements of the resolvent of quantum-mechanical Hamiltonian operators by elegantly expressing them in terms of continued fractions. In this paper we extend the recursion method to off-diagonal matrix elements of general (possibly non-Hermitian) operators and apply it to the simulation of molecular optical absorption and photoemission spectra within time-dependent density-functional and many-body perturbation theories, respectively. This method is demonstrated with a couple of applications to the optical absorption and photoemission spectra of the caffeine molecule.
authors.affiliation: SISSA-Scuola Internazionale Superiore di Studi Avanzati, I-34151 Trieste, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Baroni
authors.forename: Ralph
authors.initials: R
authors.lastname: Gebauer
authors.forename: O
authors.initials: O
authors.lastname: Bariş Malcioğlu
authors.forename: Yousef
authors.initials: Y
authors.lastname: Saad
authors.forename: Paolo
authors.initials: P
authors.lastname: Umari
authors.forename: Jiawei
authors.initials: J
authors.lastname: Xian
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D008956:Models, Chemical; D008958:Models, Molecular; D008962:Models, Theoretical; D011789:Quantum Theory